The present invention relates to densification of materials, and particularly relates to de-icing or anti-icing injection nozzles used for injecting a material into a fluid bath in a densification system.
Launch vehicles for transporting a payload into space from the Earth generally include storage tanks to store propellant for use during the launch operation. When developing and launching a launch vehicle, a balance must be struck between the amount of propellant that is included in the storage tanks and the amount of payload that can be moved by the launch vehicle. Generally, it requires more propellant to move a heavy payload, in turn requiring larger and heavier propellant tanks. Nevertheless, it is the per unit power production that is most important; a denser fuel generally provides more energy per unit volume than a less dense fuel. Moreover, if a fuel with a higher per unit energy production can be used, a greater payload can be provided for the same volume of fuel provided in the launch vehicle.
Therefore, densifying the propellants for launch vehicle use can reduce the volume of propellant needed to launch a given sized payload. Specifically, propellants can be subcooled below the normal boiling point temperature to increase the density of the propellant so that less propellant is needed to provide the same thrust or propulsive impulse to the launch vehicle. This can substantially reduce the amount of propellant needed to move a given payload. Alternatively, a larger payload can be provided when the same volume of densified propellant is substituted for a given volume of undensified propellant. Moreover, the gross liftoff weight of the vehicle can be reduced due to the lower vapor pressure of the densified propellant which results in lower tank operating pressures and reduced mass of the storage tanks.
One system for densifying a fluid is described in U.S. Pat. No. 5,644,920, entitled xe2x80x9cLiquid Propellant Densificationxe2x80x9d, incorporated herein by reference. This system can densify a propellant by directly injecting a lower boiling point fluid into a higher boiling point liquid bath to subcool the bath material below its normal boiling point temperature. A propellant can then be passed through the subcooled bath material in a heat exchanger to cool or densify the propellant during loading operations.
Other densification systems have also been developed which use turbo pumps and other complex machinery to densify the propellant. However, these systems are extremely costly and complex to operate compared to the liquid injection densification system. As a result, they greatly increase the cost of the propellant that can be provided to a launch vehicle even though the material is densified.
Densified propellants also have a greater heat capacity than undensified propellants, and therefore the vapor pressure of the propellant in the vehicle storage tanks are lower after loading operations. This results in increased propellant mass after loading and increases the payload capacity of the launch vehicle.
Therefore, it is desired to provide a system that can densify a propellant for a launch vehicle in an efficient and inexpensive manner. One drawback of the densification system described above is the propensity of the system to freeze at the injection sites, thereby reducing efficiency and requiring unplanned thaw-cycles. Therefore, it is desired to provide a densification system that can continuously densify a propellant to be provided to a launch vehicle using the liquid injection process without requiring unplanned cycling to de-ice an injection nozzle. Such a system should be able to efficiently and inexpensively densify a propellant to be used in a launch vehicle to increase the payload or decrease the amount of the weight of the vehicle dedicated to propellant storage.
The present invention is directed to a system to produce a densified propellant to be used in a launch vehicle. The system includes a bath container or vessel and an injection nozzle to inject a cooling material into the bath container. Contained within the bath container is a fluid that has a freezing temperature greater than the boiling point temperature of the cooling material injected into the bath fluid. As the cooling material is injected below the surface of the bath material, it evaporates and subcools the bath material below its normal boiling point. Surrounding the injection nozzle is an anti-icing chamber that is filled with a non-condensable gas. This non-condensable gas surrounds the injection nozzle and provides an area that is substantially free of the bath material. The cooling material injected into the bath from the injection nozzle is not injected directly into the bath material, but rather flows through the anti-icing chamber. This substantially eliminates the possibility of ice build-up on the injection nozzle as the fluid is injected from the injection nozzle into the bath material.
A first preferred embodiment of the present invention includes a cooling system to cool a first fluid with a second fluid. The system includes a vessel containing a selected volume of the first fluid. A cooling injection nozzle disposed in the vessel injects the second fluid, which is held in a coolant container, into the first fluid. A supply line interconnects the coolant container and the cooling injection nozzle. A chamber is disposed in the vessel and surrounds at least a portion of the injection nozzle. The chamber defines an opening, but substantially eliminates an influx of the first fluid towards the injection nozzle from a plurality of sides. A purge gas inlet extends from the chamber to supply a volume of a purge gas from a purge gas supply to the chamber. An interface is formed between the first fluid and the purge gas when the purge gas is supplied to the chamber. The chamber allows for a substantially maintainable and selectable temperature of the first fluid.
A second preferred embodiment of the present invention includes an anti-crystallization apparatus to substantially eliminate the formation of crystals on or in an injection nozzle. The anti-crystallization apparatus includes a chamber that defines an anti-crystallization volume and has an outlet opening. A first injection port allows a first fluid to be injected at a selected rate through the chamber and through the outlet opening. A second injection port injects a non-condensible gas into the chamber to maintain a pressure within the chamber greater than a pressure outside of the chamber. An interface is formed at the outlet opening between the non-condensible gas and an exterior fluid present adjacent an exterior of the chamber such that the exterior fluid is substantially eliminated from the interior of the chamber.
A third preferred embodiment of the present invention provides a method of densifying a material by injecting a first fluid, using an injection nozzle, into a second fluid through an anti-icing chamber. A vessel is first filled with a selected volume of the second fluid. The anti-icing chamber is placed in the vessel substantially within the volume of the second fluid. The chamber also includes an outlet opening. An interface is then formed adjacent the outlet opening. The first fluid is then injected into the second fluid through the outlet opening. The interface and the chamber substantially eliminate contact between the second fluid and the injection nozzle.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description, while indicating at least one preferred embodiment of the invention, is intended for purposes of illustration only and are not intended to limit the scope of the invention.